[MITgcm-devel] recent shelfice_remeshing push

[Jean-Michel Campin]

Hi Dan,

Thanks for looking at this.

Regarding (1), I meed to check. Fortunately I still have a clone
with branch_remeshing there, so should be able to figure out.

And reagrding (2), I made little changes in our PR #124 but kept
the main things there:
 a) S/R SHELFICE_READ_PICKUP is called in 2 places,
   1) the fisrt time in shelfice_init_depths.F, only when using remeshing,
    to read in: R_shelfice
   2) the second time in shelfice_init_varia.F , only when SHELFICEMassStepping=T.
    to read in: shelficeMass
 b) the only difference is that the fields are only read-in once,
    at the right time, instead of twice (each time the S/R was called).
    I think this is cleaner, and easier to follow.
 c) the current logic make sense to me:
    if SHELFICEMassStepping=F, we don't need to read again shelficeMass because
    it has not been updated ;
    if no remeshing, initial R_shelfice is kept to it's initial value,
    so no need to read it from pickup.
 d) there are some more complicated cases when one decide to turn on or off
    SHELFICEMassStepping and/or remeshing and try to restart from a previous 
    pickup. This is tricky, and I did not try anything that would increase
    the chances to make this kind of mixed restart successful - but nothing
    specific to these cases was there in your PR #124 neither.

Will have an update regrading (1) soon ; if not, please remind me.

Cheers,
Jean-Michel


On Tue, Dec 24, 2019 at 03:33:37PM +0000, Daniel Goldberg wrote:
> Hi Jean Michel
> 
> I have been looking through the recent commit for the shelfice_remeshing
> P/R, and have a few questions, both regarding shelfice_init_varia.
> 
> 1) I believe that in my P/R i had code under "IF (shelficeMassStepping)" to
> reinitialise ro_surf to r_shelfice if a pickup is loaded. This is because
> INIT_DEPTHS() is only called in INITIALISE_FIXED(), and so otherwise
> ro_surf will not be updated, I don't think. Do you agree, and if so, was
> this addressed elsewhere in your commit?
> 
> (also -- apologies if this code was not in my P/R. I had created a new
> branch for horizontal remeshing off of the remeshing branch; and now that i
> have removed my remeshing branch I am not sure if this change was
> reflected.)
> 
> 2) Current logic is to read from a pickup only if shelficeMassStepping is
> turned on. But remeshing can occur even when Ice shelf mass does not
> change, e.g. if initial hFac's are set as to trigger remeshing thresholds.
> (One could argue that care should be taken in initialisation, but in
> practice such situations could be difficult to avoid due to free surface
> changes.) Would it be possible to read from the shelfice pickup whenever
> remeshing is allowed?
> 
> Many thanks
> Dan

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